This application is an application filed under 35 U.S.C. Sec. 371 as a national stage of international application PCT/EP00/06937, which was filed Jul. 20, 2000.
The invention relates to a switching system which has at least one fused switch unit with a fuse link which can be switched to and fro between a switched-on position and a switched-off position.
Such a switching system furthermore has a switch for closing and interrupting the circuit of the electrical power system, as well as a switching and blocking apparatus which prevents the circuit from being closed by the switch.
The switch for closing and interrupting the circuit of the switching system is intended to make it possible to make contact with all the fuse links in the switching system without any current or voltage being applied, before the circuit of the overall system is closed. This prevents switching arcs from forming on the sensitive contacts of the fuse links, and increases the life of the fuse links.
A blocking apparatus is intended to prevent the circuit from being closed via the switch even though the fuse links are not all in their switched-on position, with the intention of preventing incorrect operations of the switching system, which can lead to the switching arcs mentioned above and to damage, in particular to the fuse link.
One object of the invention is to provide a switching system which precludes incorrect operation of the switching system in a manner which is particularly simple and cost-effective, while at the same time being very reliable.
The object is achieved by a switching system according to the invention.
According to the invention, a combined switching and blocking apparatus is provided in the switching system, with a blocking element having at least one blocking rod for each fused switch unit being mounted on an operating lever of the switch for closing and interrupting the circuit. Furthermore, an interlocking element having an opening is provided in each fused switch unit and is arranged in the fused switch unit such that it can always be switched to and fro together with the fuse link. Each blocking rod can be inserted into the opening in the associated interlocking element only when the associated fuse link is in its switched-on position; and the operating lever of the switch can be switched to close the circuit only when each of the blocking rods can be inserted into the opening in its associated interlocking element. A fuse link cannot be moved to the switched-off position when the associated blocking rod is inserted in the opening in the associated interlocking element. This is the case for all the fuse links whenever the operating lever of the switch is switched to close the circuit.
The refinement according to the invention of the combined switching and blocking apparatus automatically ensures that the circuit of the switching system cannot be closed unless all the fuse links in the fused switch units are in their switched-on position. At the same time, this ensures that, once the circuit has been closed by switching the operating lever of the switch, and hence of the combined switching and blocking apparatus, none of the fuse links can be switched from its switched-on position to the switched-off position.
Incorrect operations are thus one hundred percent precluded, with operation of the system being extremely simple by virtue of there being only one operating lever.
The switching system according to the invention may comprise just one fused switch unit. However, it preferably comprises a number of series-connected fused switch units.
The switching and blocking apparatus according to the invention is particularly applicable to switching systems having a number of fused switch units for a three-phase circuit. The fused switch units can in this case be mounted, in particular, on busbars.
The individual fused switch units may have different structural designs. For example, in one embodiment, the fuse link can be switched to and fro directly between the switched-on position and the switched-off position in the fused switch unit. In other embodiments, a fuse plug is provided for holding the fuse link, in which the fuse plug can either be switched to and fro directly between a switched-on position and a switched-off position or can be inserted into a switching rocker of a fused switch unit, which is in turn designed such that it can be switched to and fro.
The interlocking element can be mounted directly on the fuse link, but is preferably mounted on the fuse plug or on a switching rocker, so that standardized fuse links can be used without the interlocking element having to be manually released from the old fuse link and having to be mounted on the new one, when replacing the fuse link, or, in some circumstances, having to adopt complex measures to ensure that the fuse link is automatically connected to the interlocking element on replacement.
If there is a switching rocker, then the interlocking element is preferably integral with the switching rocker, in order to achieve a simple system design.
The interlocking element is preferably in the form of a guide element, which defines and monitors the switching movement of the fuse link and/or of the fuse plug or of the switching rocker, in order to ensure a uniform and exact switching process.
The interlocking element preferably has at least one latching apparatus, which engages with corresponding latching elements in the fused switch unit, when the fuse link is in the switched-off position and/or the switched-on position. The limit positions of the fuse link and/or of the fuse plug or of the switching rocker are thus fixed as defined, latched limit positions.